This invention relates to a split cell type fuel cell stack which can be used as a power source or an electric generator for various applications such as outdoor, recreation and household applications and also for a business machine and the like, and is formed into a thin type, using a solid polymer fuel cell stack which is quiet, lightweight and pollution-free.
Generally, fuel cell stacks use hydrogen as main fuel and take out the energy generated during the chemical reaction of this hydrogen with oxygen. There are several types of fuel cell stacks, and one type of them is a solid polymer electrolyte fuel cell stack. This solid polymer electrolyte fuel cell stack has features such as low operating temperature and high output density.
An example of such conventional solid polymer electrolyte fuel cell stack is disclosed in U.S. Pat. No. 5,595,834 or Japanese Patent Application No. 2001-66109 which is a patent application filed earlier by the Applicant of the present application. In such a fuel cell stack shown in FIG. 3, an anode (fuel electrode) 13a and a cathode (oxygen electrode) 13b are provided on both sides of a solid polymer electrolyte membrane 12, and an oxygen flow field plate 18 which are provided adjacent to the oxygen electrode 13b, and separator plates 34, which is provided respectively on both sides of the fuel electrode 13a and the oxygen flow field plate 18, to form the unit cell 10 by making them integral with each other. A plurality of unit cells 10 is stacked together. Such separator plates, having terminals for outputting generated power, serve as current collector plates 35a and 35b. A fuel distribution manifold 32, forming of a hydrophilic sleeve, is provided to pass through a central hole in each unit cell 10, and is in communication with the fuel electrode 13a of each unit cell, and end plates 24 are provided respectively at both end portions of a tie bolt 26, passing through the center or axis of the sleeve, to sandwich them between the two ends of the tie bolt 26, and these fuel cell components are fastened and fixed together into a unitary construction by nuts 40 and 50 via washers and O-rings 36. Such fuel cell stacks are suitable for low power fuel cell stacks, and therefore can be designed as small-sized and lightweight fuel cell stacks.
In this polymer electrolyte fuel cell stack, fuel is supplied to the fuel electrode 13a through a central portion of the nut 40, and is distributed via the hydrophilic sleeve forming the fuel distribution manifold 32.
However, the above conventional solid polymer electrolyte fuel cell stack is used as a power source of a small-size equipment or the like, and therefore need to be formed into a smaller and thinner design while maintaining high-voltage and low-current characteristics.
When it is required to generate a high voltage, it is necessary to stack many cells together, and therefore it is difficult to achieve a thin design of a fuel cell. In order that the fuel cell can be used as a power source of a business machine or the like, it is necessary t o obtain a low current with a high voltage, and it is necessary to reduce the size of the cell portion, and when the outer size thereof is thus reduced, difficulty has been encountered in the production of the fuel cell stack since fuel, i.e. hydrogen is supplied from the center axis portion.